A20B-3300-0603 Fanuc PCB Board A20B33000603 A2OB-33OO-O6O3

A20B-3300-0603 | FANUC 21i-B Pentium MMX CPU Module — 32MB DRAM / Extended Memory / Series 21i-B CNC / A20B-3300-060x Family

32MB — What the Extra Memory Provides

The A20B-3300-0603 is the 32MB DRAM variant of the Series 21i-B Pentium MMX CPU module family — doubling the working memory available to the processor compared to the 16MB A20B-3300-0602.

In the FANUC 21i-B CNC architecture, DRAM is working memory — the space where the processor executes all active code and stores all runtime data. The difference between 16MB and 32MB matters in specific circumstances:

Software option density: Each FANUC CNC software option adds executable code to the DRAM footprint. A 21i-B system with many options installed — advanced contouring, multiple spindle control, tool path graphics, multi-path coordination, servo tuning tools — places a larger software demand on working memory. 32MB provides comfortable headroom for fully-optioned configurations.

Programme look-ahead buffer: In high-speed high-accuracy machining modes, the CNC's look-ahead buffer pre-processes many G-code blocks ahead of the current cutting position. Larger look-ahead requires more DRAM. For aerospace, die-and-mould, or precision contouring applications where the 21i-B's look-ahead is pushed to its limits, additional DRAM reduces the risk of buffer constraints.

GUI and display data: The 21i-B's graphical display — tool path visualisation, programme display, diagnostic screens — stores active display data in DRAM. More complex display states demand more working memory.

Key Specifications

0602 vs 0603 — Choosing Between the Two 21i-B Pentium MMX Variants

The 060x family for 21i-B offers two DRAM options:

The processor performance is identical — both use the Pentium MMX with the same cache and clock characteristics. The difference is purely in available working memory.

When the installed 21i-B system has extensive software options, runs programmes with large look-ahead requirements, or is used for precision contouring that taxes the CNC's computational resources, A20B-3300-0603 is the preferred module.

Application Scenarios

Heavily-optioned 21i-B replacement: A Series 21i-B 5-axis machining centre with multiple software options — AICC (AI Contour Control), servo tuning, multi-axis coordination — uses A20B-3300-0603 as its CPU module to provide sufficient working memory for its full option set.

CPU module upgrade from 16MB: A 21i-B CNC with an A20B-3300-0602 (16MB) is upgraded to A20B-3300-0603 (32MB) when additional software options are installed that push the system's DRAM demand above the 16MB headroom.

FAQ

Q1: What happens if a heavily-optioned 21i-B runs with only 16MB (A20B-3300-0602) when 32MB is needed?

If active software options require more DRAM than the 16MB module provides, the CNC may fail to initialise fully, generate memory-related alarms, or refuse to load certain option functions. The FANUC 21i-B hardware manual specifies minimum memory requirements for each software option combination. Confirm memory requirements from the system's option list.

Q2: Is A20B-3300-0603 backward compatible as a replacement for A20B-3300-0602?

In most cases, yes. The additional 32MB in 0603 is purely additive — the processor remains identical, and the larger memory does not cause compatibility issues with systems designed for 16MB. The 32MB module is typically a plug-in replacement for the 16MB module with no configuration changes needed.

Q3: What is the maximum DRAM available for the 21i-B platform?

The A20B-3300-060x family tops out at 32MB (A20B-3300-0603) for the Pentium MMX generation of 21i-B modules. Later A20B-3300 series modules (such as the B3 generation with 128MB DRAM — A20B-3300-0471 confirmed for 16i-B/18i-B/21i-B) provide substantially larger memory capacity for newer system software versions that support them.

Q4: Does replacing A20B-3300-0603 affect stored CNC data?

No. CNC parameters and programmes reside in SRAM and FROM modules — separate from the CPU module. Replacing A20B-3300-0603 does not affect these stored values. After fitting the replacement, the CNC boots from FROM and reads all parameters from the intact SRAM.

Q5: Can A20B-3300-0603 serve as both a fault replacement and a memory upgrade in one operation?

Yes. If the existing CPU module has failed AND the system would benefit from additional memory, replacing a failed A20B-3300-0602 (16MB) with an A20B-3300-0603 (32MB) simultaneously resolves the hardware fault and upgrades the available DRAM. Confirm that the software version installed supports 32MB before making this upgrade.